OK, noob here.hat
I feel that as long as the M900 isnt TOO much heavier then it would be superior due to it being a light mounted inline with grip to reduce width (snagging on doorways hanks
Eli

[EDIT]: OK i got some great answers. Looks like the Gladius is nice light. What other weaponlights are comparable to the Gladiushecking

KAC vertical grip, a Gladius, and a mount will be around 10oz with batteries.  An M900 will be around 20oz with batteries.  I wanted the over 1/2 pound of weight off my rifle so I sold the M900.  I was willing to give up the 75 yard range of the M900 for the Gladius 50 yard range.  The Gladius retains the abillity to use the low level as a nav light but it does not suffer from the issue of turning itself on permanantly when wet like the M900.  When wet the M900 nav LEDs will be about as bright as the cherry of a cig each and stay on about 2 hours or so till it dries out. Plus the strobe on the gladius is cool.

Awesome. Thanks alot for the advice guys!  I am definitely going for something lightweight, and im not really worried about lighting anything up much more than 30 yards away.
I'll look into the Gladius!

Thanks again!
Eli HANKS
Eli

Gladius is the longest throwing LED based 6V light.  You could look at the Pentagon 3W lights if you dont want all the computer controlled funtions of the Gladius (strobe, low battery indicator, low level setting) and can give up a little bit of light for about 1/3 the price of a Gladius (for the handheld version Pentagon L2). They also have a version with built in secondard low level NAV LED.  The Gladius uses it s 3W LED on a low setting if you want to see where you are walking without blinding yourself.  Pentagon is on or off and there is a version that should be available soon with a 5mm LED mounted parallel to the main light.  Right now I only know of the Xenon version of the Duolight and not the 3W LED version.  

The lightest set up would be the Pentagon MS2 with integral Larue mount and push button tail cap.  Its lighter than a seperate offset Larue mount and L2 but it costs more too.  One of the local dealers can probably get you rig set up with just the features you want like the Larue offset mount instead fo the ARMS non offset mount, clicky instead of the tape switch, etc.